# Ordered pairs.

Prior to understanding what is ordered pair let us know what is a pair first.

**What is a pair?**

** **A pair is a set which have only two elements. Like {a,b} , {me,my sister}. A pair can never have more than or less than two elements ; it always have exactly two elements.

**What is ordered pair? **

A pair or set of two elements , in which order of its elements are predefined or the first element is always in first and second is always in second is known as an **ordered pair**.

An ordered pair having “a is its first element and “b” as its second element is denoted by:

{a,b}

**Equal ordered pairs:**

As , order of elements of an ordered pair is predefined ,

Two ordered pairs {a,b} and {c,d} are equal if and only if “a”=”c” and “b”=”d”

If “a” and “b” are not equal to “c” and “d” respectively the two ordered pairs cannot be equal.

**Note:**

> A pair {a,b} is equal to another pair {b,a}

For example pairs {1,2}={2,1}

>An ordered pair {a,b} is never equal to another ordered pair {b,a} unless a=b.

For example: order pairs {1,2} ≠ {2,1} but {1,1}={1,1}

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